Carlos Alcaraz edged past Ben Shelton 6-3 7-6 (3) in his first ATP Tour match since the world number one’s Wimbledon victory over Novak Djokovic.
The Spaniard will face Hubert Hurkacz in the round of 16 of the National Bank Open in Toronto after defeating the fiery American in a competitive affair.
After an even start, a break of serve in the fourth game gave Alcaraz enough of a gap to wrap up the first set in 42 minutes.
The second set was even more competitive, with neither man able to break his opponent until the world number one sealed the victory in a tiebreak.
Meanwhile, American qualifier Marcos Giron upset fifth seed Holger Rune 6-2 4-6 6-3 to set up a third-round clash with compatriot Tommy Paul.
Earlier, veteran Gael Monfils stunned Stefanos Tsitsipas 6-4 6-3, while home favourite Milos Raonic continued his resurgence by seeing off qualifier Taro Daniel 6-4 6-3.
American Mackenzie McDonald knocked out sixth seed Andrey Rublev 6-4 6-3, and second seed Daniil Medvedev is safely through after a 6-2 7-5 win over Matteo Arnaldi.
